resolve_references does not traverse list members — @ref inside list elements remain unresolved

Bug Report

resolve_references does not traverse list members — @ref inside list elements remain unresolved

Steps to Reproduce

1. Clone the repository and set up the development environment:

git clone https://github.com/regnosys/rune-python-runtime
cd rune-python-runtime
./dev_clean_setup.sh
source .pydevenv/bin/activate

2. Run the following self-contained script (no external dependencies beyond the runtime itself):

import json
from typing import List
from typing_extensions import Annotated
from pydantic import Field
from rune.runtime.base_data_class import BaseDataClass

# A keyed type — instances can be registered under an external key
class Party(BaseDataClass):
    _ALLOWED_METADATA = {'@key:external'}
    name: str = Field(..., description='party name')

# A type whose partyReference field is a @ref to a Party
class Counterparty(BaseDataClass):
    role: str = Field(..., description='role')
    partyReference: Annotated[
        Party,
        Party.serializer(),
        Party.validator(allowed_meta=('@ref:external',))
    ] = Field(..., description='reference to party')
    _KEY_REF_CONSTRAINTS = {'partyReference': {'@ref:external'}}

# Trade holds parties (the keys) and counterparties (the refs) both as lists
class Trade(BaseDataClass):
    party: List[Party] = Field(..., description='parties')
    counterparty: List[Counterparty] = Field(..., description='counterparties')

data = json.dumps({
    "party": [
        {"@key:external": "p1", "name": "Party A"},
        {"@key:external": "p2", "name": "Party B"}
    ],
    "counterparty": [
        {"role": "Party1", "partyReference": {"@ref:external": "p1"}},
        {"role": "Party2", "partyReference": {"@ref:external": "p2"}}
    ]
})

# Step A — inspect reference type after deserialize with validate_model=False
t = Trade.rune_deserialize(data, validate_model=False)
print("counterparty[0].partyReference:", type(t.counterparty[0].partyReference).__name__)
print("counterparty[1].partyReference:", type(t.counterparty[1].partyReference).__name__)

# Step B — deserialize with validate_model=True (default)
t2 = Trade.rune_deserialize(data, validate_model=True)

Expected Result

Step A: both partyReference fields are resolved to Party instances after rune_deserialize.

Step B: deserialization completes without error.

Actual Result

Step A — references are not resolved:

counterparty[0].partyReference: UnresolvedReference
counterparty[1].partyReference: UnresolvedReference

Step B — ValidationError is raised because validate_attribs re-runs model_validate on the already-constructed model and Pydantic rejects the remaining UnresolvedReference objects:

pydantic.ValidationError: 2 validation errors for Trade
counterparty.0.partyReference
  Expected either <class 'Party'> or dict but got <class 'rune.runtime.metadata.UnresolvedReference'>.
  [type=Input Validation Error, input_type=UnresolvedReference]
counterparty.1.partyReference
  Expected either <class 'Party'> or dict but got <class 'rune.runtime.metadata.UnresolvedReference'>.
  [type=Input Validation Error, input_type=UnresolvedReference]

Root Cause

BaseDataClass.resolve_references recurses only into properties that are direct BaseDataClass instances. It does not descend into list members:

# base_data_class.py — resolve_references
if recurse:
    for prop_nm, obj in self.__dict__.items():
        if (isinstance(obj, BaseDataClass)   # ← True for scalar fields only
                and not prop_nm.startswith('__')):
            obj.resolve_references(...)
        # list-valued properties are silently skipped

Trade.counterparty is a list — isinstance(list, BaseDataClass) is False, so the Counterparty items inside it are never visited and their partyReference fields remain as UnresolvedReference.

Environment

• rune-python-runtime version: 2.2.0
• Python: 3.11
• OS: macOS Darwin 25.6.0

Additional Context

Proposed fix — extend the recursion in resolve_references to traverse list members:

if recurse:
    for prop_nm, obj in self.__dict__.items():
        if prop_nm.startswith('__'):
            continue
        if isinstance(obj, BaseDataClass):
            obj.resolve_references(ignore_dangling=ignore_dangling,
                                   recurse=recurse)
        elif isinstance(obj, list):
            for item in obj:
                if isinstance(item, BaseDataClass):
                    item.resolve_references(ignore_dangling=ignore_dangling,
                                            recurse=recurse)

Impact — any Rune model JSON that uses @ref inside a list-valued field is affected:

• validate_model=False — reference silently remains UnresolvedReference; downstream attribute access fails at runtime
• validate_model=True (default) — ValidationError raised immediately, preventing use of the deserialized object